This invention relates to non-coloring, abrasion resistant coatings which adhere to and protect gold and silver surfaces without discoloration of the metal.
For a long time there has been a need to protect the surfaces of various metals from the influence of the weather and from abuse during the handling of such materials. Ordinarily, most common metals such as aluminum, steel, iron and their various alloys have been protected from corrosion by coating those substrates with greases (in the case of iron and its alloys) or by coating the surfaces with paints, clear lacquers and varnishes or by anodizing or electroplating and deposition.
Even though the above methods protect the metal substrates from corrosion to a certain degree, the form of protection, that is, the method utilized to coat the substrate cannot be uniformly used on all metal substrates. The coating of the various metal substrates usually involves the selection of the particular method of coating to also give other desirable properties such as aesthetic appearance, abrasion resistance, transparency, lubricity and the like.
One of the most common forms of corrosion protection is the coating of the metal substrates with organic or silicone coatings or various combinations of multilayers of organic and silicone coatings or copolymers thereof.
Inherent in these coatings is the problem of adhesion and this problem has been attacked many ways. For example, primers which couple the coatings to the substrates are numerous. Patent publications and other published literature abound with primer technology. These publications illustrate very well that the primers are not universal and must be matched according to the coating and the substrate utilized.
Adhesion additives have also been widely recommended and have been published on extensively. These adhesion additives function by co-reacting in-situ with the coating and then eventually co-reacting with the substrate when the coating is laid on the substrate to give the bonding effect.
Other forms of adhesion promoters have depended upon a physical attachment of various polymers to substrates and the subsequent surmounting of such polymers by the protective coatings.
All of the above methods, however, have not been sufficient to solve the problems associated with adhering coatings to the more uncommon metals such as nickel, copper, gold and silver. Special measures are usually necessary to adhere coatings to these substrates for prolonged periods of time and usually, there must be a sacrifice of some desirable properties of these uncommon metals in order to get prolonged adhesion of the coatings to them, especially the gold and silver metals.